The present invention relates to an ink jet printing system.
In a first aspect, the present invention relates to a continuous stream ink jet printing system comprising: a droplet generator for generating a plurality of streams of ink droplets, the system being constrained to the use for printing of a chosen number of droplets of each stream which is less than all of the droplets of the stream; a charge electrode in respect of each stream for selectively charging the droplets of that stream to determine which droplets are printed; control means for controlling the selective charging of the droplets by the charge electrodes; a deflection electrode in respect of each droplet stream for deflecting charged droplets of that stream; and a gutter for collecting ink droplets not used in printing.
In a second aspect, the present invention relates to a continuous stream ink jet printing system comprising: a print head comprising a droplet generator for generating a plurality of streams of ink droplets, a charge electrode in respect of each stream for selectively charging the droplets of that stream to determine which droplets are printed, a deflection electrode in respect of each stream for deflecting charged droplets of that stream, and a gutter for collecting ink droplets not used in printing; and control means for controlling the selective charging of the droplets by the charge electrodes, in the system a nominal matrix of droplet print positions being defined corresponding to the positions at which droplets can be deposited on a substrate moving at a predetermined speed relative to the print head of the system.
In a third aspect, the present invention relates to an impulse ink jet printing system comprising: a print head comprising a plurality of droplet generators each for generating in response to the receipt of impulse signals respective ink droplets; and control means for generating said impulse signals, in said system a nominal matrix of droplet print positions being defined corresponding to the positions at which droplets can be deposited on a substrate moving at a predetermined speed relative to said print head.
It is an object of the present invention to improve the quality of printing provided by prior art ink jet printing systems as described in the preceding three paragraphs.
According to a first aspect of the present invention there is provided a continuous stream ink jet printing system comprising: a droplet generator for generating a plurality of streams of ink droplets, said system being constrained to the use for printing of a chosen number of droplets of each said stream which is less than all of the droplets of the stream; a charge electrode in respect of each said stream for selectively charging the droplets of that stream to determine which droplets are printed; a deflection electrode in respect of each said stream for deflecting charged droplets of that stream; a gutter for collecting ink droplets not used in printing; and control means for controlling said selective charging of the droplets by the charge electrodes, characterized in that said control means is arranged to consider for printing from amongst a number of the droplets of each said stream greater than said chosen number with the proviso that the resultant selection made observes the said constraint.
According to a second aspect of the present invention there is provided a continuous stream ink jet printing system comprising: a print head comprising a droplet generator for generating a plurality of streams of ink droplets, a charge electrode in respect of each said stream for selectively charging the droplets of that stream to determine which droplets are printed, a deflection electrode in respect of each said stream for deflecting charged droplets of that stream, and a gutter for collecting ink droplets not used in printing; and control means for controlling said selective charging of the droplets by the charge electrodes, in said system a nominal matrix of droplet print positions being defined corresponding to the positions at which droplets can be deposited on a substrate moving at a predetermined speed relative to the print head of said system, characterized in that said control means is arranged to create a set of droplet print positions ideal for representing an image to be printed, which set is permitted to include print positions offset from print positions of said nominal matrix, at speeds of operation less than said predetermined speed, said control means comparing the positions at which droplets can be deposited at the lower speed with said set of ideal positions, said control means deciding which droplets to print in dependence on the comparison.
According to a third aspect of the present invention there is provided an impulse ink jet printing system comprising: a print head comprising a plurality of droplet generators each for generating in response to the receipt of impulse signals respective ink droplets; and control means for generating said impulse signals, in said system a nominal matrix of droplet print positions being defined corresponding to the positions at which droplets can be deposited on a substrate moving at a predetermined speed relative to said print head, characterized in that said control means is arranged to create a set of droplet print positions ideal for representing an image to be printed, which set is permitted to include print positions offset from print positions of said nominal matrix, at speeds of operation less than said predetermined speed said control means comparing the positions at which droplets can be deposited at the lower speed with said set of ideal positions, said control means deciding which droplets to print in dependence on the comparison.